Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Charles E. Reece Charles E. Reece SRF Workshop, July 11, 2005 A 100 MV Cryomodule For CW Operation A 100 MV Cryomodule For CW Operation
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Thomas Jefferson National Accelerator FacilityOperated by the Southeastern Universities Research Association for the U.S. Department of Energy
Charles E. ReeceCharles E. Reece
SRF Workshop, July 11, 2005
A 100 MV Cryomodule For CW OperationA 100 MV Cryomodule For CW Operation
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Page 2Thomas Jefferson National Accelerator Facility
6 GeV CEBAF11
CHLCHL--22
12Upgrade magnets Upgrade magnets
and power and power suppliessupplies
Two 0.6 GV linacs1.1
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Page 3Thomas Jefferson National Accelerator Facility
Cryomodule Requirements for 12 GeV CEBAF
• Voltage: ≥ 109 MV CW, 1497 MHz• Heat budget:
— 2.07 K ≤ 300 W— 50 K ≤ 300 W
• Tuner resolution: ≤ 2 Hz• FPC: 7.5/13 kW• HOM damping: Z < 6 x 108 Ω, dipoles, to avoid BBU
• Length ~8.5 m between beamline flanges
Ten new CW cryomodules are required
(26 W static, 241 dynamic, 33 W contingency)
(29 W/cavity + 9 W input couplers)
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Page 4Thomas Jefferson National Accelerator Facility
Evolution of CEBAF CW Cryomodule Design Parameters
• 1st Prototype – (SL21) installed in CEBAF South Linac
— CEBAF Cavity Shape with 2 HOM couplers
— Al-Mg Seals on beamline— 8 kW Waveguide— New Tuner Design with coarse
and fine tuning capability— Implemented space frame concept— Re-used end can design (200 W
rating)• 2nd Prototype – (FEL03) installed in
FEL— Improved piping design— Added He-II heat station to FPC
waveguides
• 3rd Prototype – (Renascence) built and ready for testing
— Implemented High-Gradient and Low-Loss cavity shapes with 4 HOM couplers
on beamline— Improved Thermal Shield Design— Incremental improvements to
vacuum vessel for fiducialization— End cans useable up to 350 W
(verified by testing)— Serpentine-shaped Al-Mg gasket
on FPC rectangular waveguide— All Al-Mg Seals (no indium)
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Page 5Thomas Jefferson National Accelerator Facility
Cryomodule Design Overview
• Cavity String • Compact beamline design enables 5.6 m active cavity length
between beamline flanges 8.5 m apart• 8 cavities with hermetic sealing valves on end of string• No inter-cavity bellows• New beamline flange design (radial wedge clamp)
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Page 6Thomas Jefferson National Accelerator Facility
Renascence-style Cold Mass
Helium circuit and cavity beamline
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Page 7Thomas Jefferson National Accelerator Facility
Flange sealing improvements
• Radial wedge clamp—Low profile for beamline flanges
US Pat. # 6,499,774
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Page 8Thomas Jefferson National Accelerator Facility
LHe Header Piping
Ti / SST Transition, 3.5”IPS
~ 5” OD Bellows, between each cavity
Return Header,5” OD SST Tube x 0.063” Wall
Supply Line, 1.5” OD SST Tube
x 0.063” Wall
~ 1.5” ID Bellows, between each
cavity
Liquid Level Standpipe
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Page 10Thomas Jefferson National Accelerator Facility
Comparison : Original & Upgrade Helium Vessels
• Two cavities per helium vessel• Five cells per cavity
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Page 11Thomas Jefferson National Accelerator Facility
Cryomodule Design Overview
• Internal support structure - Space Frame—Cold Mass Support (cavities, helium distribution, shields, …)—Cavity Alignment relative to fiducials—Roll in and out of vacuum vessel
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Page 13Thomas Jefferson National Accelerator Facility
LL Cavity System
Warm ceramic RF window
Cu-plated waveguide between RT and 2 K
l/4 waveguide RF input coupler
Piezo element (2)
Stepper motor tuner drive
Titanium helium vessel
RF reference probe
HOM coupler (4)
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Page 15Thomas Jefferson National Accelerator Facility
Mechanical Tuner 29 x 103 (2x/day, 365 day/yr, 40 yrs)Piezo Actuator 7.0 x 106 (20x/hr,24 hr/day, 365 d/yr, 40 yrs)
Radiation Limit (rads) > 106 > 108
Tuning Method Tension -Load at full stroke (kN) 14.0 ~ 22.2Travel (mm) 2 3.3
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Page 17Thomas Jefferson National Accelerator Facility
Input RF Waveguide
Renascence Waveguide
Bellows
50K Heat Station
Stiffeners
Warm Window
O-ring Groove
Protective Cover
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Page 18Thomas Jefferson National Accelerator Facility
Thermal Analysis of Input RF Waveguide
Nominal Conditions
(12GeV)
Worst-Case
Conditions(12GeV)
(Designed for 13kW)
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Page 19Thomas Jefferson National Accelerator Facility
HOM coupler probe/feedthrough
• DESY-style HOM coupler depends on resonant rejection of the fundamental.
— Qe-fundamental > 3×1011
— Typical Qe-fundamental > 1 ×1012
• Operation of the SNS cavities with CW RF had serious heating problems with the HOM couplers – probes were Cu, weak thermal conduction through the sealing dielectric.
• HOM couplers (4) were moved closer to end cells in HG and LL for maximum damping.
• The pickup probe is exposed to significant fundamental fields (10% of Hmax), so must be superconducting and thermally stabilized.
T= 2.01 K
1.E+09
1.E+10
1.E+11
0 5 10 15 20 25Eacc [MV/m]
Qo
Without Cu outputs in HOMsHeating of Cu HOM outputs+ bad feedthroughs
Field emissio
n
• Initial testing of Renascence prototypes with Cu HOM coupler probes showed serious Q degradation and long thermal time constants.
drawing
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Page 20Thomas Jefferson National Accelerator Facility
HOM coupler probe/feedthrough
• Heat load (BCS) on Nb probe in HG & LL cavity at 20 MV/m CW: — 2 - 5 mW @ 6 K— 11- 20 mW @ 8 K
• Feedthrough thermal conduction is critical• Testing and FE modeling of three designs:
Confidently better, and available< 6.9 K< 5 KJLab sapphire-
dielectric design
Acceptable and demonstrated< 9.2 K5.5 KJLab/CeramTech
design
Not viable !16 K> 13 KKyocera design used on TTF and SNS (pulsed RF)
Ttip @ 20 mW
Ttip @10 mW
RF Feedthrough Design
Used on Renascence
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Page 21Thomas Jefferson National Accelerator Facility
HOM coupler probe/feedthrough
• JLab single-crystal-sapphire dielectric HOM probe feedthroughs
JLab licensed the technology to AccelInstruments, GMBH, for commercial exploitation/application
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Page 22Thomas Jefferson National Accelerator Facility
Renascence Cavity Fabrication
• Production set—5 HG and 4 LL 7-cell cavities—RRR 347 Nb—Nb55Ti flanges and helium
vessel transition plate—Endgroups on HG and LL are
identical—Developed standard
production drawings and procedures
—Refined assembly sequence details for efficiency and QA
—Mix of internal/external shop machining
—All in-house chemistry and EBW
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Page 24Thomas Jefferson National Accelerator Facility
Microphonic detuning histogramUpgrade cryomodule SL21 in CEBAF
Cavity detuning (Hz)
σ = 1.26 Hz
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Page 28Thomas Jefferson National Accelerator Facility
Optimum Matching with Microphonics
Design optimization— Design choice for
input coupling strength (Ql) depends strongly on microphonics
< 15 Hz detuning is credible for the upgrade CM design.
With Ql of 3.4*107 ±1.5 dB, operation to 25 MV/m CW will be possible with 13 kW klystrons.
10 kW linear RF Powerfor 460 uA of beam and LL 7-cell
0 Hz
50 Hz
1 10 100
Loaded Q (10^6)
Allo
wed
det
unin
g21.2 MV/m
25 MV/m
15 Hz
19.25 MV/m
27 MV/m
25 Hz 23.5 MV/m
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Page 29Thomas Jefferson National Accelerator Facility
String Assembly
• Waveguide/window units preassembled and leak checked• String assembled - one cavity per day• No issues during assembly
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Page 30Thomas Jefferson National Accelerator Facility
Transfer of cavity string
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Page 31Thomas Jefferson National Accelerator Facility
Cryomodule Assembly
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Page 32Thomas Jefferson National Accelerator Facility
Cryomodule Assembly
Beamline mid-point
Interface between cavities
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Page 33Thomas Jefferson National Accelerator Facility
Cryomodule Assembly
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Page 34Thomas Jefferson National Accelerator Facility
Cryomodule Assembly
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Page 35Thomas Jefferson National Accelerator Facility
Cryomodule Assembly
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Page 36Thomas Jefferson National Accelerator Facility
Cryomodule Assembly
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Page 37Thomas Jefferson National Accelerator Facility
Cryomodule Assembly
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Page 38Thomas Jefferson National Accelerator Facility
Cryomodule Assembly
Sealing up vacuum tank July 7, 2005
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Page 39Thomas Jefferson National Accelerator Facility
Plans
• Renascence assembly complete this week
• Testing in JLab CMTF (17 kW CW rf available) – 6 week program begins next week
• Static heat loads – primary and shield• Qe FPC• Tuner function – mechanical and piezo• Cavity performance – Q0 vs. Eacc• Dynamic cryogenic loads – including capacity challenge• HOM Qext each port - polarization analysis, potential
count reduction• Magnetic shielding effectiveness• Microphonic analysis (accelerometers on one cavity)• Microphonic compensation test with piezo & prototype
LLRF• Installation and commissioning in September
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Page 40Thomas Jefferson National Accelerator Facility
Summary
• Renascence, the final prototype cryomodule for the 12 GeV Upgrade, has built on experience with “SL21”, “FEL03”, and the SNS production run.
• This latest version includes several design improvements
• Cavity performance spec was met in VTA tests• Assembly is complete• Documentation is in good order• Testing and commissioning now begins• We anticipate a better-than-100 MV CW cryomodule
25 MV/m x 0.7 m x 8 cavities = 140 MV, with 275 W @ 2 KA credible goal !
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Page 41Thomas Jefferson National Accelerator Facility
Acknowledgements
• Cryomodule design— Al Guerra — Joe Preble— Ed Daly— Jean Delayen— Robbie Hicks— Danny Machie— Jim Henry— Jim Takas— Tim Rothgeb
• Cavity design— Jacek Sekutowicz— Peter Kneisel— Gigi Ciovati
• Cavity fabrication— Bob Manus— Steve Manning— Rich Bundy— Sam Morgan— Larry Turlington— Gary Slack
• HOM feedthroughs— Genfa Wu— Larry Phillips— Tom Elliott
• Cavity processing and testing— John Mammosser— Danny Forehand — Byron Golden— Cliff Burden— Ralph Afanador— Isiah Daniels — Chris Graves— Pam Morrison — Joe Ozelis— Pete Kushnick
• HOM analysis— Haipeng Wang
• Microphonic analysis— Kirk Davis
• Cryomodule testing— Mike Drury— Tom Powers— Christiana Grenoble
• QA and Data Management— Brian Carpenter— Bonnie Madre— Valerie Bookwalter
• Cryomodule assembly— Kurt Macha— Jeff Saunders— John Hogan— John Fischer— Ken Worland— Jody Brock— Jim Gordon— Debbie Hedrick— Frank Humphrey— Henry Whitehead— Dave Bigelow — Leonard Page — Henry Whitehead — Mike McCrea — Charles Lassiter— Steve Dutton— Jeff Campbell